Support for Application Load Balancers

[arjunrn]

AWS just released a new Load Balancer type with support for HTTP2. There is already support for it in Cloudformation. We could have a new component likewise called Senza::WeightedDnsApplicationLoadBalancer.

[prayerslayer]

Properties of the ELB have been split up in multiple components for the ALB, and some were added.

• LoadBalancer: Basically scheme, securityGroup, subnet.
• Listener: port, protocol, certificates
• ListenerRule: Use this to forward requests to target groups based on the request path
• TargetGroup: Describes a set of EC2s along with health check config, VPC and such.

The ALB is awesome° as we could do something like this(?):

• Create ALB once with DNS record pointing to it, in separate CF stack
• Application stack contains TargetGroup for the ALB which points to its AutoScaling group (hope this works)
• Application stack also contains ListenerRule for the ALB stating when to route requests to it (e.g. for requests to /api/*

:scream:

° Somehow you can't route based on headers yet.

[arjunrn]

It might be easier to just have another component in the same stack. I don't think many microservices will have a requirement for path based routing since that would be handled in something like Skipper anyway. So just use a match all wildcard like /* and use it exactly like the Classic LB. Maybe @hjacobs or @tuxlife could pitch in as well with their opinions.

[jmcs]

I agree that it's better to have another component to avoid breaking things that are working now.

[hjacobs]

We should probably introduce a new component, but AWS guys advice us to switch to ALB for everything HTTP-based (some under-the-hood performance improvements etc).

So I would say:

• introduce new component (with "V2" suffix)
• switch default senza init templates to use the new component

We also need to support the new ELBv2 in ZMON AWS agent!

[hjacobs]

Basic support for Application Load Balancers with HTTP/2 was released in https://github.com/zalando-stups/senza/releases/tag/2.0.121

Still TODO: support ELBv2 metrics in senza health

[hjacobs]

Still TODO:

• fix healthy instances count in senza status
• fix healthy instances count in senza health

[hjacobs]

ALB/ELBv2 support should be fine in https://github.com/zalando-stups/senza/releases/tag/2.0.124